1. Field of the Invention
The present invention relates to a power plant having steam driven injector system.
2. Discussion of Background
The final object of improvements to power plants is always to minimize the emissions of harmful substances from combustion and to maximize the efficiency of the plant. Attention is drawn, in this respect, to the gas-turbine groups of the newer generation which can furnish efficiencies of more than 35%. A further well-developed technique in power plants is to employ so-called combination plants. By this expression is meant the operative cooperation of a gas-turbine group with at least one downstream steam-turbine circuit, the exhaust gases from the gas-turbine process, which still have a relatively high energy potential, being conveyed into a waste-heat steam generator, in which the generation of the steam necessary for loading a steam turbine takes place. Such a waste-heat steam generator can be a single-pressure or mixed-pressure appliance. It is possible, furthermore, to equip the waste-heat steam generator with additional firing. According to the current state of the art, such a plant can furnish efficiencies of well above 55%. It is obvious that efforts are aimed at developing further these fossil fueled power plants, firstly with a view to a better utilization of the fossil reserves and secondly in light of the fact that, from the predetermined platform, any technological advance, by leverage, makes a difference which is out of all proportion in economic terms. In the case of gas-turbine groups, an appreciable fraction of the turbine power has to be expended in order to drive the compressor, and therefore an increase in the pressure drop in the gas turbine, leading per se to a higher efficiency yield of the plant, is to be achieved by a higher compression of the working air in the compressor and consequently provides little or nothing in terms of the end result, for the positive power from the turbine is lost in the form of an increased absorption of the shaft power by the compressor.
EP-A1-0,462,458 disclosed a method for increasing the compressor-related pressure drop of the gas turbine of a power-generating machine. In this method, the circuit consists of a gas-turbine group and of a downstream waste-heat steam generator. An injector takes effect immediately upstream of the combustion chamber, and the air precompressed in the compressor flows through the suction nozzle of said injector. The driving nozzle of this injector is loaded by at least some of the steam occurring in the waste-heat steam generator, with the result that the compressor air is further compressed, this taking place without taking up a fraction of power from the gas turbine. This orientation affords the sought-after increase in efficiency, with the proviso that combustion takes place in the combustion chamber by means of a gaseous fuel. If, in contrast, a liquid fuel is employed, it is necessary to adopt additional auxiliary measures with regard to the gasification of this fuel, and these largely nullify again the resulting increase in efficiency arising from the further compression of the air via an injector. A simple injection of a liquid fuel by atomization does not provide the low NOx values, such as are desired today. Nor does an admixture of steam assist here to the desired extent.